.mainpagebox{
    /* background: yellow; */
   /* display: flex; */
   /* flex-direction: row;
   flex-wrap: nowrap;
   justify-content: center; */
}
.asidemenu{
    /* width: 200px; */
    min-height: 400px;
    /* background: yellow; */
    float: left;
}
.contextBox{
    width: 900px;
    padding: 15px;
    min-height: 400px;
    /* background: blue; */
    float: left;
}

.testbox{
    position: fixed;
    width: 100%;
    height: 100%;
    top:0;
    left: 0;
    z-index: 5;
    background: rgba(0,0,0,0.2);
    display: flex;
    justify-content: center;
    align-items: center;
}
.sbox{
    width: 200px;
    height: 100px;
    border: 1px solid blue;
    background: #fff;
}